The Sanger Antipodal Bomber with a top speed of 13,000 mph was intended to fly around the earth with a series of "skips" (dives in and out of the atmosphere).

Around 1960, there was a serious engineering proposal to develop an orbital X-15 using Navaho boosters to launch the vehicle into a once around orbit with a 400,000 foot apogee and a 250,000 foot perigee.

There is a very desirable goal between pop-up sub orbital and orbital flight.
TUI has proposed a space tether system that in one variation can pick up a payload (up to 30,000lbs) from a 100km altitude and mach 12, and fling it into LEO. This works both ways of course and can de-orbit as well. They have produced some engineering studies www.tethers.com/papers/HASTOLAIAAPaper.pdf and www.tethers.com/papers/JPC00HASTOL.pdf. Their plans seem sound and realistic.
Although their system proposes liftiing a payload from the launch plane, small craft such as the ones that compete for the Xprize could be lifted straignt into orbit. I suggest that the next Xprize be for a craft to attain the same height as the first prize but at a horizontal velocity of mach 12, (about 9,000 mph).

I too find this concept very interesting and economical - it's providing infrastructure.

There is more than one concept like this. One HASTOL-studiy is to be read at the NIAC-site and ijn one of the elevator-topics at this board someone has given a link to a czech site of a team that wants to llift a payload up to 30 km by something like an electrical helicopter and then to pick it up by tether from orbit.

Several variations of that concept seem to be possible - I have to add RASCAL. An article under www.xprizenews.de has reported that RASCAL will use the feather-technique of Scaled. The article said too that RASCAL will shoot a small payload into LEO once it has reached a certain high launch altitude. I could imagine that this payload could be picked up in LEO to get into HEO or on an interplanetary course.

All this could be of great use in the future and perhaps manned vehicles or at least capsules might reach an orbit this way.

But I wouldn't call that a "goal between suborbitil flight and orbit" - I would call it a link between the both kinds of flights or a connection between them. It's like transporting something to a hand-over-point by one service and receiving it there by another service as used by normal transportation companies on earth.